Modern sewerage systems are often inspected for breaks, cracks, spalling of pipe, poor joints, and other defects by using waterproof video equipment mounted on a mechanical device which can be remotely operated while it crawls along sewerage pipes, or is towed on a skid or skate. Of course, it has been long recognized, that organic matter is undergoing decomposition within the confined spaces such as found within a sewerage system. Decomposition of organic matter may proceed with the generation of various gases, some of which may be toxic to humans, and some of which may be explosive when in sufficient concentration. Human toxicity of these gases may be aggravated by the low oxygen concentration expected in the sewerage system. Often, before entering a manhole, personnel must wait until the space has been ventilated mechanically for a period of time, and must then test the area for gases. Partly for this reason it is typically required that at least two people work together when entering a sewerage system, and that those entering wear a safety harness.
Additionally, there is some concern in the industry that the concentration of certain gases may rise sufficiently within the sewerage system to produce an explosive mixture. This concern relates to pipe crawler devices which may generate a gas igniting spark through their electrical or mechanical components. Because of industry concern, the possible establishment of standards is being explored to require that remotely controlled pipe crawlers be fabricated incorporating “explosion proof” technology, which is intended to substantially reduce or eliminate the risk of spark generation by the device. Such explosion proof equipment will be more difficult to manufacture, and consequently will be more expensive.